Question 57 QMED02 - Electrician-Refrigerating Engineer

The Correct Answer is B **Explanation for B (prevent the fire from spreading by the conduction of heat):** When a fire is contained within a compartment (like on a ship or in a structure), the metal bulkheads, decks, and overheads surrounding that compartment absorb massive amounts of heat. This heat is then transferred through the metal structure via **conduction**. If the temperature of the unexposed side of the bulkhead (the side not facing the flames) rises sufficiently, it can ignite combustible materials stored or present in the adjacent compartment. Cooling the bulkheads and decks prevents this conducted heat from raising the temperature in adjacent compartments high enough to cause secondary fires, thus stopping the spread of fire. **Why the other options are incorrect:** * **A) cool the metal below its ignition temperature:** Metals do not have an "ignition temperature" in the way flammable solids or liquids do; they melt or oxidize (rust) at high temperatures but do not combust. The goal is not to cool the metal below its own ignition point, but to cool it so it doesn't ignite materials next to it. * **C) prevent oxygen from reaching the flames:** Cooling the exterior bulkheads does not directly control the oxygen supply inside the burning compartment. Methods like smothering (using CO2, foam, or boundary cooling *to reduce heat to the fire*) or sealing the compartment prevent oxygen from reaching the flames. * **D) form a dense coating of smothering steam:** While boundary cooling uses water, the primary function is heat absorption, not creating a "dense coating of smothering steam." Steam is created, but it generally escapes into the atmosphere or drains away. Furthermore, steam is primarily a smothering agent when injected directly into the fire space, not when applied to the exterior surface of the boundaries.